package org.ghost.springboot.demo.component.sharding;

import io.shardingjdbc.core.keygen.KeyGenerator;
import io.shardingjdbc.core.keygen.TimeService;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.util.concurrent.ThreadLocalRandom;

public class GhostGenerator implements KeyGenerator {
    private static final Logger logger = LoggerFactory.getLogger(GhostGenerator.class);

    private static TimeService timeService = new TimeService();
    /**
     * 基础时间(一旦确定不能变动)
     */
    public static final long EPOCH = LocalDateTime.of(2017, 1, 1, 8, 0, 0).atZone(ZoneId.of("Asia/Shanghai")).toInstant().toEpochMilli();
    /**
     * 机器标识位数
     */
    private final long workerIdBits = 5L;
    /**
     * workerId最大值11111 -> 31
     */
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

    /**
     * 数据标识位数
     */
    private final long datacenterIdBits = 5L;
    /**
     * datacenterId最大值11111 -> 31
     */
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    /**
     * 毫秒内自增位
     */
    private final long sequenceBits = 12L;
    /**
     * 毫秒内最大并发值11111111111 -> 4095
     */
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    /**
     * workerId左移位数12
     */
    private final long workerIdShift = sequenceBits;
    /**
     * datacenterId左移位数17
     */
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    /**
     * 时间戳左移动位22
     */
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;


    private long workerId;

    /**
     * 数据标识id部分
     */
    private long datacenterId;
    /**
     * 并发控制
     */
    private long sequence = 0L;
    /**
     * 上次生产id时间戳
     */
    private long lastTimestamp = -1L;

    public GhostGenerator() {
        this.datacenterId = getDatacenterId(maxDatacenterId);
        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }

    /**
     * @param workerId     工作机器ID
     * @param datacenterId 序列号
     */
    public GhostGenerator(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new RuntimeException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new RuntimeException(
                    String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    /**
     * <p>
     * 获取 maxWorkerId
     * </p>
     */
    private static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (StringUtils.isNotEmpty(name)) {
            /*
             * GET jvmPid
             */
            mpid.append(name.split("@")[0]);
        }
        /*
         * MAC + PID 的 hashcode 获取16个低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /**
     * <p>
     * 数据标识id部分
     * </p>
     */
    private static long getDatacenterId(long maxDatacenterId) {
        long id = 0L;
        try {
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            if (network == null) {
                id = 1L;
            } else {
                byte[] mac = network.getHardwareAddress();
                if (null != mac) {
                    id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
                    id = id % (maxDatacenterId + 1);
                }
            }
        } catch (Exception e) {
            logger.warn(" getDatacenterId: " + e.getMessage());
        }
        return id;
    }

    /**
     * 获取下一个ID
     *
     * @return
     */
    @Override
    public synchronized Number generateKey() {
        long timestamp = timeService.getCurrentMillis();
        if (timestamp < lastTimestamp) {//闰秒
            long offset = lastTimestamp - timestamp;
            if (offset <= 5) {
                try {
                    wait(offset << 1);
                    timestamp = timeService.getCurrentMillis();
                    if (timestamp < lastTimestamp) {
                        throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                    }
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            } else {
                throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
            }
        }

        if (lastTimestamp == timestamp) {
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 同一毫秒的序列数已经达到最大
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 不同毫秒内，序列号置为 1 - 3 随机数
            sequence = ThreadLocalRandom.current().nextLong(1, 3);
        }

        lastTimestamp = timestamp;

        if (logger.isDebugEnabled()) {
            logger.debug("timestamp:{},datacenterId:{},workerId:{},sequence:{}", timestamp, datacenterId, workerId, sequence);
        }

        return ((timestamp - EPOCH) << timestampLeftShift)    // 时间戳部分
                | (datacenterId << datacenterIdShift)           // 数据标识部分
                | (workerId << workerIdShift)                   // 机器标识部分
                | sequence;                                     // 序列号部分
    }

    private long tilNextMillis(long lastTimestamp) {
        long timestamp = timeService.getCurrentMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = timeService.getCurrentMillis();
        }
        return timestamp;
    }
}

